1. Field of the Invention
The present invention relates to surveying instruments, and more particularly to a measurement referencing and transferring instrument that enables a user at a working location to sight a selected point on a remote object, and to transfer the selected point along a sighting axis in the opposite direction onto another object, to facilitate measurements associated with the remote object.
2. Description of the Known Art
Surveying instruments having either an optical viewing system or a laser device for emitting a collimated light beam, are generally known. Such instruments tend to be expensive and, in most cases, meet only one particular application. The known transits, levels and laser instruments can perform their intended tasks quite well; however, their individual design configurations tend to limit each instrument to its own special use.
U.S. Pat. No. 4,291,982 issued Sep. 29, 1981, discloses a multi-purpose surveying instrument for use as a theolodite to survey inclinations, a horizontal plane or angles, and to survey perpendicularity or vertical angles. The instrument has a single sighting telescope that rests on an instrument base with leveling tubes. The instrument base is fastened atop an adjusting base having a set of leveling screws, and the adjusting base in turn is mounted on a tripod in a conventional manner.
U.S. Pat. No. 3,918,813 issued Nov. 11, 1975, describes an optical viewing alignment unit for use in a telescope gun sight, wherein the gun sight is aligned by auto-collimation. The collimator includes a light source, lens, and a graticule with the axis of the collimator perpendicular to a non-reflecting side of a beam splitting cube. Light from the collimator including a datum line image enters the cube and is split vertically to appear in the telescope eyepiece, and to exit through a window of the gun mount to a target.
A construction laser for providing a number of detectable reference lines, is described in U.S. Pat. No. 4,333,242 (Jun. 8, 1982). A housing of the laser is supported on feet that are attached to the housing through a motor driven alignment and leveling device. Further, U.S. Pat. No. 4,973,158 (Nov. 27, 1990) discloses a rotating laser beam plane instrument for use in the surveying and construction industries. The instrument provides a plane of laser light which acts as a position reference when detected by portable electronic detectors. Another instrument for providing a rotating laser beam in a horizontal plane, is shown in U.S. Pat. No. 4,993,161 issued Feb. 19, 1991.
It is also known to project a laser beam from the base of a geodetic instrument toward a defined ground mark, for purposes of plummeting. U.S. Pat. No. 5,159,760 issued Nov. 3, 1992, shows a laser collimator built in an upper plate of a tribrach which supports a theolodite on a tripod. A light beam from the collimator passes through an opening in a lower base plate of the tribrach, to align the instrument over a ground mark such as a boundary stone, according to the patent.
U.S. Pat. No. 3,355,979 (Dec. 5, 1967) discloses an optical device that enables one to determine the line of sight between two fixed points. U.S. Pat. Nos. 4,852,265 (Aug. 1, 1989) and 5,075,977 (Dec. 31, 1991) show devices capable of emitting laser light beams in vertical directions for plummeting.
Leveling lasers comprising a laser diode built into a precision construction level are known, wherein the diode projects a beam of light from one end of the level to provide a visible laser dot on a surface up to 100 feet away. Such leveling lasers are available, e.g., from Edmund Scientific Company, Barrington, N.J.--Stock Nos. J52,201-3.
A need has arisen on the part of home owners, building contractors and other trade persons involved in the building repair and construction fields, for a relatively inexpensive but nonetheless accurate sighting and surveying instrument capable of performing a number of measurement and referencing tasks, and which can be readily set up for use in the field.